(1) Field of The Invention
The present invention relates to an improved process for the preparation of 2-fluoro-9-(2,3,5-tri-O-benzyl-beta-D-arabinofuranosyl) adenine (I). In particular the present invention relates to a process wherein a protected fluoroadenine is reacted with a protected chlorosugar to improve the yields and reduce the cost of the desired compound (I).
(2) Prior Art
U.S. Pat. Nos. 4,188,378; 4,210,745 and 4,357,324 to Montgomery or Montgomery and Shortnacy, Montgomery et al, J. Med. Chem. 12, 498-504 (1969) and J. Het. Chem. 16, 157-160 (1979) describe various procedures for the preparation of 2-substituted-9-(2,3,5-tri-O-benzyl-beta-D-arabinofuranosyl) adenine compounds wherein the 2-substituent can be converted to a fluoro group. The problem is that the fluorination step in the 2-position is difficult and produces low yields. Since the cost of the protected sugar is high, the low yield (.apprxeq.37%) of the 2-fluoronucleoside significantly impacts the cost of the final product which is 9-beta-D-arabinofuranosyl-2-fluoroadenine or the 5'phosphate.